From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752048AbaHRGdz (ORCPT ); Mon, 18 Aug 2014 02:33:55 -0400 Received: from cantor2.suse.de ([195.135.220.15]:52193 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752002AbaHRGdx (ORCPT ); Mon, 18 Aug 2014 02:33:53 -0400 From: NeilBrown To: Ian Kent Date: Mon, 18 Aug 2014 16:33:01 +1000 Subject: [PATCH 4/5] autofs4: d_manage() should return -EISDIR when appropriate in rcu-walk mode. Cc: autofs@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <20140818063301.9860.65391.stgit@notabene.brown> In-Reply-To: <20140818062844.9860.43007.stgit@notabene.brown> References: <20140818062844.9860.43007.stgit@notabene.brown> User-Agent: StGit/0.16 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If rcu-walk mode we don't *have* to return -EISDIR for non-mount-traps as we will simply drop into REF-walk and handling DCACHE_NEED_AUTOMOUNT dentrys the slow way. But it is better if we do when possible. In 'oz_mode', use the same condition as ref-walk: if not a mountpoint, then it must be -EISDIR. In regular mode there are most tests needed. Most of them can be performed without taking any spinlocks. If we find a directory that isn't obviously empty, and isn't mounted on, we need to call 'simple_empty()' which does take a spinlock. If this turned out to hurt performance, some other approach could be found to signal when a directory is known to be empty. Signed-off-by: NeilBrown --- fs/autofs4/root.c | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c index 2296c8301b66..71e4413d65c8 100644 --- a/fs/autofs4/root.c +++ b/fs/autofs4/root.c @@ -433,8 +433,6 @@ static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk) /* The daemon never waits. */ if (autofs4_oz_mode(sbi)) { - if (rcu_walk) - return 0; if (!d_mountpoint(dentry)) return -EISDIR; return 0; @@ -452,12 +450,28 @@ static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk) if (status) return status; - if (rcu_walk) - /* it is always safe to return 0 as the worst that - * will happen is we retry in REF-walk mode. - * Better than always taking a lock. + if (rcu_walk) { + /* We don't need fs_lock in rcu_walk mode, + * just testing 'AUTOFS_INFO_NO_RCU' is enough. + * simple_empty() takes a spinlock, so leave it + * to last. + * We only return -EISDIR when certain this isn't + * a mount-trap. */ + struct inode *inode; + if (ino->flags & (AUTOFS_INF_EXPIRING | AUTOFS_INF_NO_RCU)) + return 0; + if (d_mountpoint(dentry)) + return 0; + inode = rcu_dereference(dentry->d_inode); + if (inode && S_ISLNK(inode->i_mode)) + return -EISDIR; + if (list_empty(&dentry->d_subdirs)) + return 0; + if (!simple_empty(dentry)) + return -EISDIR; return 0; + } spin_lock(&sbi->fs_lock); /*